Acoustic device



ACOUSTIC DEVICE Filed M z ay 15, 1925 4 Sheets-Sheet l Feb. 16, 1932. c,WARNER 1,845,733

. ACOUSTIC DEVICE Filed May 15, 1925 4 Sheets-Sheet 2 55 his fltto'm qsI Feb. 16, 1932. W RNER 1,345,733

ACOUSTIC DEVICE Filed May 15, 1925 4 SheetsSheet 3 Feb. 16, 1932. cWARNER 7 1,845,733

ACOUSTIC DEVICE Filed May 15. 1925 4 Sheets-Sheet 4 awumtoz 67/6 /7155/Y "WK/V57.

a hi awn/nu s UNITED STATES PATENT OFFICE CHARLES N. WARNER, O]? miwYORK, N. Y.

ACOUSTIC DEVICE Application filed Kay 15, 1925. Serial No. 30,415.

This invention relates to acoustic apparatus such as to recordingdevices recording and reproducing sound boxes of talking machines, totelephone receivers and transmitters and other devices in which adiaphragm or a flexing element is utilized and which is responsive to orsets up sound Waves and is a continuation in part of my copendingapplication Serial No. 738,155, filed September 8, 1924. The inventionis particularly valuable in connection with telephone receivers of thetype popularly known as loud speaking telephone instruments which arewidely employed in connect-ion with radio sets. -This inventionrelatesparticularly to an improved diaphragm for use in such instruments andalso to an improved generating system in conjunction therewith.

Faulty reproduction is traceable almost wholly to acoustical, notelectrical, causes,

' these being due to the inherent shortcomings of the diaphragms, cones,etc., and their associated driving mechanisms used to trans lateelectric impulses into sound waves. It is the limited capacity of thediaphragm to generate overtones which prohibits its use as a vibratoryfactor in original musical instruments, and it is this same overtonalinadequacy which renders it incapable under forced vibration to res ond'fully and perfectly to the entire complex range of incoming electricalimpulses that correspond to the original overtones. By employing themost perfect vibratory system ever deviseda two point suspended andtensed elementto take up and vibrate to the electric impulses'and thusrepeat the sound waves emanatin from the original instrument, and byusingin conjunction therewith a liquid seal diaphragm to act as theresonator to amplify the vibrations thus generated (the only resonatorever invented which will notefi'ect an unnatural dissipation of theovertones given off by the generator)-by using this the most perfect ofall vibratory systems this device embodies principles so fundamentalthat without them perfect reproduction will forever remain impossible.

An object of the invention is to provide an improved'acoustic devicewhich, when utilized for the reproduction of sound waves, will producesuch sound waves with a better balancing of the diflerent parts orcomponents, such as, for example, the different voices or instrumentsmaking up a rendition; and which will produce sound waves of purer,clearer and more natural tone and quality; and with which thesequalities may be varied at will to some extent.

A further object is to provide an improved acoustic device with which'sympathetic vibrat-ions of the parts thereof will be substantially orentirely eliminated; and with which less distortion of the reproducedsound waves will be obtained and fewer sounds foreign to the desiredreproduction created. A further object is to provide an improvedacoustic device which may be given different characteristics to suit thedifferent effects desired; and with which the reproduction of soundwaves will be free from various extraneous noises and distortion,particularly those noises in radio loud speakers, which are commonlyascribed to so-called static.

A further object is to rovide a sound box and a diaphragm'there or whichis readily adaptable for use in conjunction with talking machines, loudspeakers, microphones, and the like, which is durable, non-resonant, notaffected by atmospheric changes; that will improve the quality of toneemitted or transmitted or recorded and will also reproduce and transmitwith increased volume lower tones than have heretofore been possible.

A further object is to provide sound-functioning apparatus in which thegenerating or flexing element is separate from the resonating member ordiaphragm, not only to render possible the use of diaphragms ofdifi'erent sizes, but also and in particular to permit the embodiment ofa vibratory means for performing the eriodic motion in a manneranalogous to tiat performed b the string the vibratory means employe inthe finest musical instruments, and which alone is susceptible ofinfinitely varied complex harmonic vibration.

A further object of m invention is to provide a sound box for te ephonereceiving instruments in which the diaphragm, the generating and voicingelement, and the armature are three separate parts.

Magnetic materials suitable for diaphragms such as are generally usedare relatively heavy; heretofore it has been necessary to make asacrifice in lightness of diaphragm, which would produce the bestacoustic efficiency, in favor of magnetic qualities. With this improvedconstruction the armature can be made of good magnetic material and ofsuificient thickness to readily conduct steady and alternating fluxesfrom one core to the other in abipolar receiver, thereby giving the bestefliciency of the oscillatory force per unit of electric energyreceived. The generatin or voicing element consists of a strip of exiblematerial rigidly supported at its two ends at opposite points of the rimof the casing and connecting means of tensing; this generatin elementserves two purposes: first, it holds the diaphragm or vibratoryreproducing element and armature in the correct operative positions; andsecondly, by its proper proportions in conjunction with a variable meansof tensing thereby afiords a practical means to approximate the correctacoustical properties entirely independent of the size of the diaphragm.

Another object is the elimination of sympathetic vibrations in acousticapparatus, and the revention thereby of extraneous noises anddistortion, one of the chief causes of which is the restriction of theperiphery of the diaphragm. This distortion is most noticeable whenstrong signals are being received.

A further object of this invention is the practical elimination of theaudible reproduction of static. 1

Among the features of the invention are, first: the employment of adiaphragm of a new type-one that does not flex at anypoint within itsplanethe vibrations being conveyed to it by an attached auxiliarytwopoint suspended and tensed generating element, preferably thin, andunder a variable tension and means to ap ly said tension at either end.This means flor tensing the generating element is also utilized toproperly center the diaphragm in a correct 0 erative position. Thediaphragm is provi ed with a flange which sets in a well in the casingand in the devices which permit the diaphragm to be operated in ahorizontal position, in which an inelastic fluid, suchas water, verythin oil, or any other substance in that state in which the particlesmove fieely among themselves, remain in one mass, and always take theform of the'containing vessel, is used as a sealing means for separatingthe front from the back sound waves because of offering practically noresistance to the diaphragms movements, this kind of substance afiordingalso an excellent damping agent. In such a diaphragm mounting-with thepulse has a tendency to cause the diaphragm to execute a series ofvibrations. This diaphragm is, therefore, practically non-resonant,which is important, because, if it is elastic and resonant it stores upenergy when forcibly flexed to either side of its medial line, and whenreleased would vibrate in accordance with its fundamental tone therebybeing detrimental to the faithful reproduction of speech and music. Withthis construction of diaphragm the air displacement is the same over itsentire surface, with the result that the overtones are more faithfullyreproduced.

In those devices to be used on phonographs where the diaphragm has to beoperated when in a vertical position, vaseline and like substanceshaving suflicient surface tension and adhesive qualities which serves tohold them in place without the necessity of a containing means, is used.v

The invention also contemplates various other features which will appearfrom the following description of various embodiments of the invention.

In the accompanying drawings Fig. 1 is an elevation of a radio loudspeak-' er and telephone receiver constructed in accordance with theinvention;

Fig. 2 is a sectional elevation through the re 'roducing unit of thesame;

ig. '3 is a plan of one section of the unit, the other section beingremoved;

Figs. 4 to 7 are modified forms of flexing element;

1'1 8 is a sectional elevation through a soun box also constructed inaccordance with the invention and of the typeparticularly adapted foruse with talking machines;

Fig. 9 is a plan of the same;

Fig. 10 is a plan of a similar unit with a magnetic armature provideddirectly upon the tensioned flexing member;

Fig. 11 is a sectional elevation of the same;

Fi 12 is a plan of a. tensioned flexing mem er which may be employed inthedevice of Figs. 8 and 9 or 10 and 11;

Fig. 13 is a plan of another unit also constructed in accordance withthe invention and in which the bridge member is magnetically actuated;and

Fig. 14 is a sectional elevation of the same.

Referring first to the embodiment of the strum ent.

The casing is mounted by the boss 2 upon a cabinet 3, which serves as abase for the in- The cabinet 3 has a sound conduit 4 which communicateswith the smaller end of an upright horn 5 of any suitable construction,so that sound waves set up by the receiving mechanism within the casing1, will be conducted to the horn 5, amplified thereby, and dischargedinto the room. hen the sound producing mechanism within the easing 1 isof the telephone receiver type, the,

instrument is popularly known as a loud speaking receiver.

The casing 1 is made of two sections 6 and 7, the lower section 7 beingshown in Fig. 3. The tubular boss 2 extends from the end wall of thelower section 7. The two sections are normally secured together in anysuitable manner, such as by screws or bolts, but may be separated topermit access to the mechanism within the same.

A flexible strip 8 of spring material, such as spring metal, or anyother suitable flexible material, is formed in any suitable manner, inthis instance being of the shape shown in Fig. 4. The ends of the bridgemember are connected by screws 9 to the ends of pins or rods 10 whichextend through slidable bushings 11 in the lower section 7 of thecasing, the projecting end of each pin or red being threaded andcarrying a nut 12 which abuts against the outer face of the casing. Thebushings 11 may be held against sliding movement in the casing in anysuitable man ner such as by set screws 11a carried by the casing andengaging opposite sides of each sleeve. Thus by rotation of either orboth of the nuts 12, a tension may be produced upon the bridge member 8within the plane of the latter, the degree of tension of which isvariable depending upon the extent of rotation of the nuts 12. Theflexing bridge member 8 is provided with a central aperture 13 throughwhich a screw, bolt, or rivet 14 may pass, the latter also passingthrough an armature disc 15 and a diaphragm 16,

which may be disposed respectively upon 0pposite faces of t e tensionedflexin member. W'ashers 17 may be disposed between the bridge member andthe armature and diaphragm so as to space the same. Suitableelectromagnetic actuating devices 18 may be mounted in the upper section6 of the casing, with the magnet polar ends 19 projecting into proximityto the armature 15 so as to insure a. magnetic pull thereon, dependingupon thedegree of permanent magnetism in the electroma netic device 18.The diaphragm is preferab y disposed upon the side of the flexing bridgemember toward a flat wall of the lower casing section 7, but slightlyspaced therefrom, so that there will be a thin layer of air in the spacebetween the diaphragm and the said end wall of the lower section 7 ofthe casing.

The diaphragm may be made of any suitable material, and for this purposeamong the metals I have found aluminum to be very satisfactory, since ithas the advantage of both relative lightness and rigidity. Heretoforealuminum has been unsatisfactory for diaphragms because it did not havesuflicient elasticity, and when flexed and vibrated as usual heretoforeit produced very flat hollow and unsatisfactory sounds, instead of thefull round resonant tones which are usually sought. In accordance withthis construc tion, however, aluminum is advantageous since because ofits lightness,-it will have little inertia, and because of its largelypistonlike action it is not open to the objection which has heretoforeexisted.

The diaphragm may also be made of paper, bakelitc, or other suitablematerial, and is preferably coated with a very viscous semiliquidmaterial of great internal friction or viscosity, which renders itpractically incapable of sympathetic vibration.

The end wall of the lower section 7 of the casing is provided with anannular channel or well 20, which receives a quantity of a substance 21in that state in which the particles move freely among themselves,remain in one mass, and always take the form of the containing vesselsuch as very thin oil, water, and like substances having these samecharacteristics. The diaphra 'm is provided with an angular peripheralflange 22 which extends part way into the well or channel 20 and intothis inelastic fluid substance 21. This substance 21 serves as anairtight closure for the periphery of the diaphragm,

without materially restricting the movements of the diaphragm with thebrid e. This substance also acts as a very slig tly resistant seal forthe flange of the diaphragm.

When an undulating current passes through the electromagnets of thedevice 18, a variable magnetic pull will be created upon the armature15, and this pull will cause a concomitant vibration of the tensionedflexing member, having a frequency in character tially purecondensations and rarefactions,

and will be free of the distortions usually caused when a diaphragm isrestrained at its periphery and flexed conically as heretofore. Byadjusting the nuts 12, the tension in the flexing bridge member 8 may bevaried to some extent, and I have found that by the variations in thetension of the same, the characteristics of the reproduction may bevaried to a considerable extent.

By providing the fluid seal for the periphery of the diaphragm, themaximum loudness is obtained for the sound waves created by minorvibrations of the diaphragm, as this v fluid seal oflers very littleresistance to the ment. The thin layer of air between the diaperipheralportion of the dia hragm, and therefore is conducive to its free om ofmovephragm and wall of the casing serves as'a cushion for the diaphragmmovements which will prevent blasting when the vibration rate becomesvery high. The sound waves set up by the dia hragm are conducted throughthe tubular oss 2, through the conduit 4 of the base 3, and thence intothe horn '5 where they are amplified and discharged into the room.

In Fig. 5 a flexing member 8a is illustrated, which is provided withsubstantially circular center portion and tongue-like extensions ondiametrically opposite sides, and which may be tensioned by thetensioning means shown in Figs. 1 and 2.

In Fig. 6 a somewhat similar flexing member 86 is illustrated, havingfour extensions by which it may be tensioned by the devices shown inFigs. 2 and 3.

.In Fig. 7 a circular flexing member 80 is illustrated, having threeextensions by which it may be tensioned, the tensioning extensions beingdisposed at 120 degrees apart around the periphery of the same.

In Figs. 8 and 9 another embodiment of the invention is illustrated, theapplication of the invention to a talking machine sound box beingparticularly illustrated. In this embodiment of the invention the soundbox 23 is provided with a sound wave exit passage 24 leading from a wallthereof, and also is provided with an annular well or channel 25receiving a viscous sealing substance having a surface tension andadhesive qualities sufficient that it be retained in well 25 when thediaphragm is in an operative vertical position.

The flexing bridge member 27, similar to the member 8 of Figs. 1 to 3,is anchored at one end to the casing in any suitable manner, such as bya screw 28 and an abutment block 29.- The flexing member passes throughaslot 30 ot'the casingand through a slot in the abutment member 29. Thescrew 28 passes through a portion of the casing, through an aperture inthe end of the bridge member 27 which is within the abutment member, andis in threaded engagement with the abutment member. The abutment memberengages the periphery of the casing and thus serves to anchor that endof the bridge -,member against endwise movement.

The other end of the flexing member is connected by a screw 31 and awasher 32 to I a block 33, which is slidable radially in the toan extentdepending upon the extent of desired.

A diaphragm 35 is secured, at an interior point such as at the center,by a screw 36 and spacer washer 37 to a point of the flexing memberbetween the ends of the latter, that is at a point in its span.Preferably the connection between the diaphragm and the flexing memberis made at a point between the center of the span of the flexing memberand one of its ends, that is, not at the center of the span of theflexing member. In stringed instruments, the string is never stroked atits exact central point and I have found that better results areobtained when the connection between the diaphragm and the flexingmember is similarly made, that is, at one side of the center of thespan.

The diaphragm may be of any suitable material and corresponds todiaphragm ,16 of Figs. 1' to 4. The diaphragm is spaced slightly fromthat'wall of the sound box having the sound wave exit opening 24, andmay have an annular angular flange 38 which enters the well or channel25 and engages with the sealing substance 26 thereof as in the precedingembodiment.

W hen the sound box is used for recording or transmitting purposes, thetransmitter button or recording stylus is connected either directly orthrough leverage or linkage to the flexing member, preferably to thesame point of connection as that to the diaphragm. In Figs. 8 and 9,however, the flexing member is arranged for actuation by a lever 39which is mounted for rocking movement on suitable adj ustable pivots 40of the casing. This lever either carries an armature by which it may bemagnetically actuated, or a recording'stylus 41 which is vibrated whenit runs in sound grooves, as well known in talking machines.

The flexing bridge member 27 is preferably enlarged and formed in theshape shown in Fig. 9 for the reason that such a shape has been found togive excellent results, but it will be understood, of course, that theflexmg member may be made of other shapes or arranged to be tensioned atdifferent points as has been explained, for example, in connection withFigs. G and 7. The flexing member may be made of any suitable spring or.

any other flexible material, the same as the flexible bridge member 8 ofFigs. 1 to 4.

Referring particularly to Figs. 10 to 12 I have illustrated a similarform of sound box, in which the diaphragm and flexing member areintended for electromagnetic actuation, the tensioning means for thebridge member being also slightly modified. In this embodiment of theinvention, the sound box 42 has the sound wave exit opening 43 as in Figs. 8 and 9. The flexing member 27, corresponding to the bridge memberwith the same reference numeral in Figs. 8 and 9, passes through a slot.in the sound box wall, and through a slot 44 in an abutment member 45which engages with the periphery of the sound box. 4

A locking pin 46 passes through an aperture 47 in the projecting end ofthe flexing member, so that when the flexing member is tensioned, itwill draw the pin 46 against the abutment member 45 and the latteragainst the periphery of the sound box. The other end of the flexingmember is connected, by a screw 47 and-washer 48, to one end of a rod 49which projects through a bearing sleeve 50 and through an abutment block51 engaging with' the periphery of the sound box. The sleeve 50 may beadjustably held in different positions by suitable means, such as by setscrews 52 carried by the sound box and engaging with said sides of thesleeve 50. A nut 53 is threaded upon the projecting end of the rod 49,so that when rotated upon the rod 49, it will act against the abutment51 and, through the pressure of the latter against the sound boxperiphery, will draw the rod 49 outwardly and tension the flexing memberwithin its plane.

A diaphragm 54, corresponding to the diaphragm 35 of Figs. 8 and 9, issecured by a screw 55 to the flexing member, at a point in the span ofthe latter between its center and points of anchorage of its ends, as inFigs. 8 and 9. The diaphragm may have an annular angular peripheralflange 56 which engages with a sealing substance 57, corresponding tothe substance 26 of Fig. 8, which substance is carried in awell orchannel 58, so that the periphery of the diaphragm will be unrestrainedin vibration except for the slight resistance offered by the sealingsubstance in the channel or well.

A disc 59 of magnetic material, such as soft iron, may be secured to theflexing memberupon the opposite face thereof from the diaphragm, in anysuitable manner such as by the screw 55 which anchors the diaphragm tothe flexing member, and suitable spacer.

washers 60 may be interposed between the flexing member and thediaphragm and armature disc.

In Figs. 13 and 14 a somewhat similar construction is provided, in whichthe armature disc is avoided. and the flexing member is made of magneticor magnetically-responsive material. such as silicon steel or othermagnetic material commonly employed for the diaphragms of telephonereceivers or the armatures of electromagnets. In this form of theinvention, the flexing member 61 is anchored at one end upon a threadedstud 62 which is carried by a. strip 63, secured between two sections"64 and 65 of the sound box and projecting into the interior of the box.A

' second strip 66 extends over the stud 62 and the flexing member, andalong the strip 63, so as to confine the bridge member upon the stud 62.The two strips 63 and 66 are secured together and to the section 65 ofthe sound box by a screw 67 which passes through the two strips and hasthreaded engagement with the section 65 of the sound box. A nut 68 maybe threaded upon the free end of the stud 62 so as to securely clam thetwo .strips 63 and 66 to the flexing mem er at the point of connectionthereto.

' The other end of the flexing member 61 passes through a slot 69 in thesound box casing and through a slot in an abutment member 70. A lockingpin 71 is passed through an aperture 72 in the projecting end of theflexing member, so as to anchor the flexing member to the abutmentmember. One end of the abutment member is pivoted at 73 upon one of thescrews (not shown) which passes between and connects the two sections 64and 65 of the sound box casing. A stud 74 passes through and is threadedin the other end of the abutment member 70, and at its inner end has aball-shaped tip 75 which engages in a concave cavity 76 in theperipheral wall of the casing, so that whenever the stud 74 is rotated,it will engage with the sound box casing, and that end of the abutmentmember 70 will be cammed outwardly to exert longitudinal tension uponthe flexing member. The stud 74 may have a head 77 by which it may berotated in either direction.

A diaphragm 78, similar to the diaphragm 54 of Figs. 10 and 11, issecured by a screw 79 to the flexing member as in the precedingembodiments. The diaphragm 78 has a peripheral flange 80 engaging in awell 81, carrying inelastic fluid sealing substance 82. A

permanent magnet 83 of the horse shoe or ring type is secured within onesection 64 of the casing, and is provided with polar ends 84 whichextend into proximity to the bridge member at opposite sides of thescrew 79 which connects the flexing member to the diaphragm.

The polar ends 84 have the usual electromagnets 85 mounted thereon andincluded in the telephone circuit, so that when an undulating current ispassed through the electromagnets 85, the flexing member will bemagnetically vibrated in accordance with the undulations of the current.The flexing member being of magnetic material will, of course, respondto the variable magnetic field or pull which is caused by the undulatingcurrent in the electromagnets. and the diaphragm will be correspondinglyvibrated with the flexing member.

The diphragm is connected at an interior 12 the variable tension hasbeen applied to the shorter section of the span from-the point ofconnection to the diaphragm, in Figs. 13 and 14, the adjustabletensioning means is connected to the longer'section of the span.

When a device constructed in accordance with the invention is used as atelephone receiver, the electromagnets of the receiver mechanism willexert a pull upon the flexing member tending to flex the same, and asthe current in the electromagnets fluctuates, the pull upon the flexingmember will likewise fluctuate. By reason of the tension and elasticityof the flexing member, it will always tend to move away from theelectromagnets when the current therethrough decreases or is in adirection to neutralize the magnetic pull and, therefore, the flexingmember will vibrate in accordance with the undulations of current in thecontrolling circuit.

to the flexing member, it will be given a substantially perfect pistonaction, which is acknowledged as the most desirable form of vibration ifthe most perfect acoustical result is to be obtained. The two diflerentmaterials used as sealing means in the two different classes of devicesillustrated-one, an inelastic fluid substance such as very thin oil,water, etc.; and the other a substance such as Vaseline being retainedin operative position by the surface tension and its natural adhesivequalities well known thereof; both of these substances prevent theescape or entrance of displaced air peripherally of the diaphragm ateach piston movement and,

therefore, sound waves of considerable intensity will be set up duringthe minor vibra tions of the diaphragm, where the air dis-t placement isslight.

At the same time, especially in those devices which will permitthe usewhen in operative position of the diaphragm in a horizontal position,the sealing means will offer practically negligible resistance to thediaphragm vibration. The sealing means will also, together with thecoating of the diaphragm, prevent vibrations of the diaphragm or partsthereof which are not caused by and which do not correspond to thefluctuations of the'undulating current, or of the movements of thestylus in the case of a talking machine. The flexing member'is placedunder tension from opposite points, preferably substantiallydiametrically opposite, and it has been found that the characteristicsof reproduction or operation of the mechanism may be varied to someextent by varying the tension of the flexing member.

The flexing member, because it is tensed and combined with the diaphragmwhose inherent vibrations are damped, does not respondreadily to minorvibrations which are caused by static and extraneous noises and,therefore, furnishes the most practical method of eliminating theaudibility of such annoyances.

From the various examples which have been given, it will be observedthat in reproducing instruments, the flexing member may be vibratedbylevers or linkage, or directly by a magnetic pull, but it will also beobvious that many of the advantages of these constructions will accruewhen the diaphragm is operated by impinging sound waves, and themovements of the flexing member and diaphragm resulting therefromutilized either to make sound records, or in the creation of anundulating current as in microphones and other transmitting telephonicinstruments it is also equally apparent that the tensed bridge membershown and described may be utilized to drive any desired type ofreproducing vibratory element of which various lands are well known.

- It will be obvious that various changes in the details, which havebeen herein described and illustrated for the purpose of explaining thenature of the invention, may be made by those skilled in the art withinthe principle and scope of the invention as expressed in the appendedclaims. 1

I claim 1. In an acoustic device, a support, a vibratory elementconnected to said support, a substantially rigid diaphragm connected tosaid vibratory element, and an inelastic fluid c0- acting with the freeperipheral edge of the diaphragm and aflording little resistance to itsmovement.

2. In an acoustic device, a sound box comprising a casing with a soundwave exit, a substantially rigid diaphragm disposed'over said exit, anda receptacle in said casing provided with .an inelastic fluid for thereception of the peripheral portion of said diaphragm.

3'. In acoustical apparatus, a support, a diaphragm-held in operativeposition, and inelastic fluid means in said support co-operating'withthe periphery of said diaphragm to dampen the movement of saiddiaphragm.

4. A diaphragm mounting comprising a support, a diaphragm, an inelasticfluid in said support in contact with the peripheral portion of saiddiaphragm.

5. An acoustic reproducing device having only one flexing member, saidflexing member having a len h equal to at least'twice any of its otherimensions and supported only at its two ends, and means for tensioningsaid flexing member inthe direction of its length.

6. An acoustic reproducing device comprising only one flexing member forperforming the periodic motion, said flexing member III being made ofone piece of material having a length equal to at least twice any of itsother dimensions and connectedly supported only at its two ends, andmeans for tensioning said flexin member in the direction of its length.

7. i n acoustic reproducing device for the conversion or translatingelectromagnetic variations into sound or sound waves intoelectromagnetic variations, comprising a magnetic actuating means, aflexing member of magnetic material having a length equal to at leasttwice any of its other dimensions supported only at its two ends, andmeans for tensioning said flexing member in the direction of its length,said actuating'means act ing directly on said flexing member.

8. In an acoustic device, a support, a bridge member anchored at itsends to said support, a diaphragm connected at an interior point to saidbridge member at one side of the center of the span of said bridgemember, whereby when the bridge member and diaphragm vibrate togetherthe bridge member will be flexed.

9. In an acoustic device, a support, a flexible member anchored at itsends to said support, a diaphragm connected at an interior point to saidflexible member, at one side of the center of the span of said flexiblemember, whereby when the flexible member and diaphragm vibrate togetherthe bridge member will be flexed, and means for tensioning sa d flexiblebridge member in the direction of its length.

10. In an acoustic device, a support, a bridge member anchored at itsends to said support, a diaphragm connected at an interior point to saidbridge member at one side of the center of the span of said bridgemember, whereby when the bridge member and diaphragm vibrate togetherthe bridge member will be flexed, the anchorage of at least one end ofsaid bridge member being adjustable to place the bridge member undervariable tension within its plane.

11. In an acoustic device, a support, a bridge member connected to saidsupport, a diaphragm connected to said bridge member, and an inelasticfluid for coacting with the free peripheral edges of the diaphragm.

12. In an acoustic device, a support, a bridge member connected atopposite ends to said support and under-tension within its plane, adiaphragm connected to said bridge member, and a substance in that statein which the particles move freely among themselves, remain in one mass,and always takes the form of the containing means, for coacting with thefree peripheral edges of the diaphragm.

13. In an acoustic device, a support, a bridge member carried by thesupport, a diaphragm connected at an interior point to said bridgemember at a point in the span of the same, and a substance in that statein point to said bridge member at a point in the span of the same, meansfor actuating the tensed flexing member and through it the diaphragm,and an inelastic fluid carried by the support and engaging with the freeperiphery of the diaphragm, so as to offer little resistance to thepiston-like movements of the diaphragm.

15. In an acoustic device, a support, a flexible bridge member connectedunder tension within its plane to said support, a vibratory reproducingelement connected to said bridge member for vibration therewith, andmeans for vibrating said bridge member.

16. In an acoustic device, a support, a bridge member connected undertension within its plane to said support, a diaphragm connected to saidbridge member for vibration therewith, means for vibrating said bridgemember, and a substance having appreciable fluidity carried by thesupport and engaging with the free periphery of the diaphragm.

17. In an acoustic device, a support, a bridge member, means foranchoring the ends of the bridge member to the support under tension,said anchoring means permitting the placing of variable and desiredtensions upon said bridge member, a free edge vibratory reproducingelement connected to said bridge member, and means for vibrating thebridge member.

18. In an acoustic device, a casing having a sound wave opening in awall thereof, a spring bridge member carried by the casing, a diaphragmconnected at an interior point to the bridge member at a point in thespan of the same and extending substantially parallel to and slightlyspaced from said wall, said casing having a channel carrying a substancehaving an appreciable fluidity, wit-h which substance the'free peripheryof the diaphragm engages.

19. In an acoustic device, a casing having a sound wave opening in awall thereof, a spring bridge member carried by the casing under tensionwithin its plane, a diaphragm connected at an interior point to thebridge member at a point in the span of the same, and extendingsubstantially parallel to and slightly spaced from said wall, saidcasing having a channel carrying a substance having an appreciablefluidity with which substance thefree periphery of the diaphragmengages.

20. In an acoustic device, a casing having a sound wave opening in awall thereof, a spring bridge member, means for anchoring the ends ofthe bridge member to the casing,

and adjustable to place the bridge member under "ariable tension withinits plane, a diaphragm connectedat anv interior point to the bridgemember at a point in the span of the latter, and extending substantiallyparallel to'and slightly spaced from said well,

which substance the free said casing having a channel carrying asubstance having an appreciable fluidity, with phragm engages.

21. In an acoustic devlce, a support having a channel therein, aninelastic fluid in said channel, a substantially rigid diaphragm, meansfor mounting said diaphragm from its interior on said support, saiddiaphragm hav ing a free peripheral portion entering said channel andengaged by said substance.

22. An acoustic device, comprising a casing having a wall provided witha sound wave opening therethrough, said wall having a channel, adiaphragm having a peripheral angular flange entering said channel, asubstance having appreciable fluidity disposed in said channel andengaging with the flange of the diaphragm, and means connected to aninterior point of the diaphragm for support means comprising a springbridge memberto the span portion of which the interior 7 point of thediaphragm is connected.

24. An acoustic device, comprising a casing having a wall rovided with asound wave opening theret rough, said wall having a channel. a diaphragmhaving a peripheral angular flange entering said channel, a

substance having appreciable fluidity disposed in said channel andengaging with the flange of the diaphragm, means connected to aninterior point of the diaphragm for supporting the latter for vibrationtoward and from said wall, said supporting means comprising a springbridge member to the span of, which an interior portion of the diaphragmis connected, and means bywhich said bridge member may be vibrated.

25. An acoustic device, comprising a casing having a wall provided witha sound wave opening therethrough, said wall having a channel, adiaphragm having a peripheral angular flange entering said channel, asubstance having appreciable fluidity disposed in said channel andengaging with the flange of the diaphragm. means connected to anperiphery of the dia interior point of the diaphragm for supporting thelatter for vibration toward and from said wall, said supporting meanscomprising a spring bridge member to the span of which an interiorportion of the diaphragm iscon- ,nected, and means for placing saidbridge member under tension within its plane.

26. An acoustic device, comprising a casing ing the". bridge memberunder variable tension within its plane.

27. 1 An acoustic device, comprising a casing having a wall providedwith a sound wave 0 ening therethrough, said wall having a -c annel, adiaphragm having, adjacent its periphery,

an angu ar flange entering saidchannel,asubstancehavingappreciablefluidity disposed insaidchannel andengaging with the flange of the diaphragm, and means including a bridgemember connected to an in-' terior portion of the diaphragm forsupporting the latter for vibration toward and from said wall, theconnection between the diaphragm and bridge member being at a section inthe span at one side of the central point of the span.

28. In acoustic apparatus, a sound box com- I prising a casing with asound wave exit, a free edge vibratory reproducing element disposed oversaid exit, and a spring bridge member secured to said element and to theperiphery of the said casing.

29. In acoustic apparatus, a sound box comprising a casing with asoundwave exit, a

free edge vibratory reproducing element disposed over said exit, aspring bridge member secured to said element and to the periphery of thesaid casing, and means adapted to tension the said spring bridge member.

30. In acoustic aparatus, a sound box comprising a casing with a soundWave exit, a diaphragm disposed over said exit and having a flange onits outer rim, a receptacle in the said, casing for the said flange, anda spring bridge member secured to the said diaphragm and to the saidcasing.

31. In acoustic apparatus, a sound box comprising a casing with a soundwave exit, a diaphragm disposed over said exit and having a flange onits outer rim, a receptacle in the said casing 'for the said flange, aspring bridge member secured to the said diaphragm and to the saidcasing, and means adapted to tension the said spring bridge member.

32. In acoustic apparatus, a sound box comprising a casing with a soundwave exit, a diaphragm disposed over said exit and having a flange onits outer rim, a receptacle in the said casing provided with slightlyresistant airtight closure means for the rece tion of the said flange,=as ring brid e mem r secured to the said diap ragm an to the said casing,

and means adapted to tension the said spring bridge member. p

33. In acoustic apparatus, a sound box comprising a casing with a soundwave exit, a diaphragm disposed over said exit and having a flange onlts outer rim, a receptacle in the said casin for the said flange, aliquid like substance in the said receptacle, a spring bridge membersecured to the said diaphra and to the said casing, and means to tenslonthe said spring bridge member.

' 34. In acoustic apparatus, a soundbox comprising a casing with a soundwave exit, a diaphragmdisposed over said exit and having a flange on itsouter rim, a receptacle in the said casing for the said flange, a jellylike substance in the said receptacle, a spring bridge member secured tothe said diaphra and to the said casing, and means to tension the saidspring bridge member.

35. In acoustic apparatus, a sound box comprising a casing w1th asoundwave exit, a

prising a casing with a sound wave exit, a iaphragm disposed over saidexit and having a flan e, a spring element secured to the said diap ragmand the said casing, means adapted to tension the said spring element,whereby the said diaphralgm is free to vibrate but is rendered practicaly incapable of flex-- 40. In acousticapparatus, a sound box comprising acasing'wlth a sound waveexit, a diaphragm disposed over said exit andhav- 39.- In acoustic apparatus, a sound box coma mg a flange on itsouter rim, a receptacle in x the said casing for the said flange, asprin element secured to the said diaphragm an the said casing, andmeans-adapted to tension the said spring element whereby the saiddiaphragm is free to vibrate but is rendered practlcally inca able offlexing.

In witness w ereof, I hereunto subscribe my signature.

CHARLES N. WARNER.

diaphragm disposed over the said exit, and I a reed secured to the saiddiaphragm and to the said casing.

36. In acoustic apparatus, a-sound box comprising a casing with a soundwave exit, a

diaphragm di osed over said exit and havmg a rectangu ar flange, areceptacle in the sald casing containing an inelastic fluid and adaptedfor the reception of the sald flange, and a reed secured to the saiddiaphragm and to the said casing.

is free to vibrate but is rendered v diaphra practically incapable offlexing.

38. In acoustic apparatus, a sound box comprising a casing with a soundwave exit, a

diaphragm disposed over said exit and having a ange, a receptacle in thesaid casing provided with a fluid airtight closure means for thereception of the said flange, a spring se-' cured-to the said diaphraand to the said casing, anld mians t1azdap to tension the said spring were y e said dia hra to vibrhte but is rendered pradticafi? bleof-flexing. v a

is free incapa-

